Scientists from the University of Toronto have found a link between moral disgust and the natural disgust we feel when we see something gross or taste something bad. The researchers discovered that we make the same facial movements in response to all three types of disgust—namely, moving the levator labii muscle, which raises the upper lip and wrinkles the nose in what is called an "oralnasal rejection response." In their study participants showed activity in this muscle region when they tasted unpleasant liquids, looked at disgusting photographs, or were treated unfairly during a game.
Our disgust response evolved to help us avoid things that make us sick, like poisonous plants and disease. The new research suggests that our reaction to immoral behaviors—which we sometimes say are "sick" or "leave a bad taste" in our mouths—evolved from these earlier forms of disgust.
According to cognitive psychologist Adam Anderson who worked on the project, the “results shed new light on the origins of morality, suggesting that not only do complex thoughts guide our moral compass, but also more primitive instincts related to avoiding potential toxins. Surprisingly, our sophisticated moral sense of what is right and wrong may develop from a newborn’s innate preference for what tastes good and bad, what is potentially nutritious versus poisonous.” —Heather Wax